Assignment 4
Due data 10/10/2008
1. Suppose I chose 10 students at random from the class, ask their age and record this an
integer( discrete variable). Which of the following must be true?
A. The mean must be an integer since the data is.
B. The median must be an integer since the data is.
C. The sample must be random since I chose the students are random.
D. All of the above must be true.
E. None of the above have to be true.
2. Which of the following best describes a simple random sample of size n ?
A. All n observations have different values
B. All possible samples of size n are just as likely
C. All possible values of the population are just as likely
D. All n observations have the same value
E. Random implies it cannot be determined
3. There may be a “gender gap” in political party preference in the U.S., with women more likely than
men to prefer Democratic candidates. A political scientist selects a large sample of registered voters,
both men and women. She asks every voter whether they voted for the Democratic or the Republican
candidate in the last congressional election. Is this an observational study or an experiment? Why?
What are the explanatory and response variables?
4. The National Halothane Study was a major investigation of the safety of anesthetics used in surgery.
Records of over 850,000 operations performed in 34 major hospitals showed the following death rates
for four common anesthetics.
Anesthetic A B C D
Death rate 1.7% 1.7% 3.4% 1.9%
There is a clear association between the anesthetic used and the death rate of patients. Anesthetic C
appears dangerous.
4a. Is this an observational study or an experiment?
4b. Is this sufficient evidence to say Anesthetic C causes more deaths? Why or why not?
